1. Field of the Invention
This invention relates to a variable-wavelength light source apparatus used for evaluating and manufacturing an optical communication system and an optical device.
2. Description of the Related Art
Hitherto, a variable-wavelength light source (a tunable laser source) capable of varying a wavelength of output light has been used as a main component for outputting test signals to test an optical part in measurement, adjustment, study, etc., of the optical part. FIG. 3 shows a configuration example of an optical parts measurement apparatus 100 for measuring optical characteristics of an optical part using a variable-wavelength light source according to a related art.
The optical parts measurement apparatus 100 comprises a variable-wavelength light source 101, an optical coupler 102, optical fibers 103, 104, and 105, and an optical power meter 107. The optical coupler 102 has three output terminals 108, 109, and 110 and the output terminal 108 or 109 is connected to the optical power meter 107 by the optical fiber 104. The output terminals 108 and 109 can be selectively connected to the optical power meter 107. In case of connecting the optical power meter 107 to the output terminal 109, the intensity of an optical signal output from the variable-wavelength light source 101 to the optical coupler 102 is measured. In case of connecting the optical power meter 107 to the output terminal 108, the intensity of a light reflection signal input to the optical coupler 102 as return light reflected from a device under test 106 is measured. The device under test 106 of an optical part is connected to the output terminal 110 by the optical fiber 105.
When an optical signal is output via the optical fiber 103 from the variable-wavelength light source 101, the optical signal is branched through the optical coupler 102 to the output terminals 109 and 110. The optical signal branched to the output terminal 109 of the optical coupler 102 is input via the optical fiber 104 to the optical power meter 107 previously connected to the output terminal 109 (if the optical fiber 104 is connected to the output terminal 109 rather than the output terminal 108). The intensity of the optical signal output from the variable-wavelength light source 101 is measured with the optical power meter 107.
The optical signal branched to the output terminal 110 is input via the optical fiber 105 to the device under test 106 and is transmitted, reflected, or scattered by various optical elements provided in the device under test 106. The light reflection signal reflected by the device under test 106 is again input to the optical coupler 102 via the optical fiber 105.
The light reflection signal input to the optical coupler 102 is output to the output terminal 108 of the optical coupler 102. The optical fiber 104 and the optical power meter 107 connected to the output terminal 109 are changed to connection to the output terminal 108 from connection to the output terminal 109, whereby the light reflection signal is input to the optical power meter 107 via the optical fiber 104 and the intensity of the light reflection signal is measured. The previously measured intensity of the optical signal from the variable-wavelength light source 101 is compared with the intensity of the light reflection signal of return light from the device under test 106, thereby measuring a light reflection attenuation amount of the device under test 106. Measuring is repeated while a wavelength of the optical signal output from the variable-wavelength light source 101 is changed, whereby wavelength characteristic of the light reflection attenuation amount of the device under test 106 can be measured.
The variable-wavelength light source 101 according to the related art contains a gas cell for wavelength calibration (not shown), whereby the wavelength of the optical signal output from the variable-wave-length light source 101 is monitored, is measured, and calibrated.
However, in relation to the variable-wavelength light source according to the related art, when the optical part is measured, the external power meter needs to be attached through the optical coupler and connection of the optical power meter must be changed at each time measurement. The measurement takes labor and time and is cumbersome, and thus this is a problem.
The variable-wavelength light source needs to output an optical signal having a longer wavelength and an optical signal having a shorter wavelength with high precision and high accuracy of an optical part in recent years. Thus, it is a problem that the gas cell for wavelength calibration contained in the variable-wavelength light source according to the related art cannot deal with longer or shorter wavelengths. In case of using an external gas cell for wavelength calibration capable of dealing with long and short wavelengths, an additional external optical power meter, etc., needs to be installed. Thus, it is problem that this takes labor, time, and costs.